Process of working up mixed shavings of white metal and red metal



Patented Dec. 17, 1929 UNITE STTS ANTON'SGHWARZ, OF BERLIN-WEIDMANNSLUST, GERMANY PROCESS OF WORKING UP MIXED SHAVINGS F WHITE METAL ,AND RED METAL No Drawing. Application filed June 10, 1927, Serial No. 197,994, and in Austria. May 5, 1926.

chanical mixture of white and red metal accrues. The mixed shavings contain, according to their origin, as white metals: bearing metals, tin solder, type metal and the like, and also metallic lead or tin, or mixtures of 0 any or all of these substances. The red metal shavings consist of copper alloys, such as bronze, red brass, pinchbeck, brass, or even metallic copper.

The usual treatment of the mixed shavings is effected by heating the mixture of shavings until the white metal is completely melted out, and then removing from the melt the red metal shavings, which only melt at considerably higher temperatures, azrather considerable quantity of white metal still remaining adhering to the red metal shavings. The red metal shavings are melted down separately. The white metal which remains in the melting vessel, and which is enriched with copper, is cast into blocks. In the case of this method of working some such products as the following are obtained, for example, from a mixture containing 16 per cent of red metal and 84 per cent of white metal 62% white metal with a medium copper content (about 6% Cu) 8% white metal with a rather high copper content (about 20% Cu) 20% speculum metal (with a content of about to Cu, 3 to 15% Pb, and 20 to 40% Sn) 10% ash.

As will be seen from these figures this method of working is not economical, since the melting of the white metal results in the formation of fresh alloys in an undesirable direction. The white metal' takes up considerable proportions of copper, whereas the "red metal forms alloys with the constituents of the white metal, with tin and lead. A

white metal is obtained, which, on account of its considerable percentage of copper, is only less useful for many purposes, and on the other hand speculum metal, which can only be employed to quite a small extent as an addition to special alloys, such as alloysfor bell metal and the like. In order not to leave this by-product'unused, the speculum metal is for the most part blown in a converter to metallic copper, the tin-and lead being removed in the form of their oxidation products.

Now the present process enables red metal and White metal to be obtained separately from the mechanical mixture without the composition of the shavings being materially altered. In the case of this process also, the mixture of white and red metal shavings is heated to a temperature at which the red metal shavings, which have a higher melting point, are notmelted. The essence of the new process consists in the fact that the melt, after carrying out this heating, is subjected during slow cooling to a very careful selective disintegration, in which the brittle particles of white metal are brought to a finer grain than the particles of red metal, and can therefore be separated from the latter by me chanical methods, such for example as sifting. Use is preferably made, as a means for the selective disintegration, of a scouring operation, the hard red metal turnings preferably serving at the same time as scouring elements.

It has further been found that the process can be carried out with remarkable success if the mixture of turnings and the like is only heated up to the melting point of the eutectic of the white metal or, if there are several eutectics, up to the melting point of the eutectic having the highest melting point. By this means the eutecticmixtures which connect the crystal grains are melted, whereas the crystals embedded in the eutectic mixture are still unmelted. During the subsequent mechanical treatment of the mixture of turnings with slow cooling, in a scouring drum for example, the white metal becomes brittle, and can readily be disintegrated. For this mechanical treatment use may be made for example of a rotating drum. The hard red metals then exert a grinding action upon the soft white metal. This action can be further strengthened by equipping the rotating drum with beaters or the like, or by constructing it eccentrically.

In order to prevent the pulverized white metals from caking together, graphite or Wood charcoal may be added to the mixture of shavings. Other substances, such forexample as fluorspar, heavy spar, clay, French chalk, magnesium oxide, and also wood-dust, fatty oils, tar or the like have been found suitable for this purpose. These substances have the common property of also at the same time preventing the formation of alloys between red metal and white metal up to from 500 to 600 0., or at least of making such formation more difiicult. By the majority of these additions the metals are also protected against oxidation.

The process is preferably carried out in the following manner: To the mixture of turnings is added from 0.1 to 3 per cent of graphite, and the mixture is then heated in a rotatably supported drum up to the melting point of the eutectic of the white metal, or, if the alloy contains a plurality of eutectics, up to that temperature at which the eutectic with the highest melting point melts. This temperature lies in general, according to the composition of the white metal alloys, between150 and 330 C. The heating is now discontinued, and the drum, equipped, if desired, with beaters, is rotated, and at the same time the material is cooled down below the melting point of the eutectic having the lowest melting point, whereby the temperature falls in general below 15 degrees. By the mechanical treatment the white metal is ground down to ,a fine powder. After the termination of the scouring, which proceeds with continued cooling, the drum is stopped. The red metal shavings, the composition of which has remained unaltered, can now be easily separated from the white metal powder, preferably by sifting.

Another form of the process consists in heating the mixture of red metal and white metal turnings, with the addition of substances which prevent the formation of alloys, up to a temperature at which the white metal is completely'melted, withdrawing the greater portion of the molten white metal, and subjecting the remainder of the mixture during cooling to a selective disintegration, preferably to scouring. In this form the addition of graphite or of substances which at the same time prevent the formation of alloys is an absolute necessity.

For the carrying out of this modification of the process the mixed shavings are heated, with the addition for example of from 0.1 per cent to 3 per cent of graphite, preferably in a rotatable drum, until the white metal is completely melted. This is the case, according to the composition of the white metal, at a temperature of from 230 to 600 C. Notwithstanding this comparatively high temperature there is no formation of alloys worth mentioning between the red metal and the white metal. At most there takes place at the surface an absorption of lead by the red metal, amounting to a maximum of from 0.1 to 0.6 per cent of lead. The molten white metal is drawn off, and the red metal shavings remain in the drum, together with a still considerable percentage of white metal. The drum and its contents are now slowly cooled down to 150 degrees, and the portions of white metal still present are powdered and can then easily be separated from the red metal. The white metal powder obtained ac cording to the invention is melted and cast into bars or ingots. The yields of the new process, in the case of a mixture of the proportion hereinbefore assumed of 16 per cent red metal. and 8% per cent white metal are as follows 16% red metal shavings which are practically free from lead;

78% White metal with the same copper content as the initial material;

6% ash.

Even more favourable yields have repeatedly been obtained. Hence according to this new process the whole of the red metal is recovered practically unchanged, whereas the losses in ash are at the expense of the white metal, but are less than with the known process. Furthermore, not only is a. higher yield of white metal obtained, but it is obtained above all in the original composition, so that the occurrence of waste alloys, which can only be utilized with difliculty, if at all, is obviated by the new process.

Examples 1. As an initial material, 150 kilograms of a mixture containing 30 per cent of red metal turnings and per cent of white metal turnings was employed. The analysis of the red metal turnings gave the following result:

10.1% Sn; 87.7% Cu; 0.35% Pb; 0.1%

Fe; remainder Zn.

The white metal turnings show the composition 40.2% Sn; 3.2% Cu; 15.1% Sb; remainder Pb.

This material was introduced into a rotatable drum, and with it was mixed 1 per cent of siderite graphite, the mixture being heated, with the drumrotating, up to 240 C. After attaining this temperature the heating was discontinued, the drum was cooled during further rotation for about three-quarters of an hour, and then emptied, the material being separated by sifting into red metal turnings and white metal powder. The following result was obtained from this method of working:

30% red metal shavings of the composition:

10.2% Sn; 87% Cu; 0.55% Pb; 0.1% Fe; remainder Zn;

and

66.9% of white metal in bars of the com-- position 40.1% Sn; 3.2% Cu; 15.0% Sb; remainder Pb.

The loss'in the form of ash amounting to 3.1%

II. The same quantities of the same initial material, with the addition of 2 per cent. of graphite were heated in the rotating drum up to 450 0., the molten white metal was then drawn oil, and the rest of the material remaining in the drum was further treated as in Example I. The yield amounted to 30.1% red metal turnings, and

66% white metal in bars, after melting down together the main part of the white metal first drawn ofi' and the residual powder.

The analysis of thered metal turnings yielded the following values 103'}? Sn; 66.6% Cu; 0.7% Pb; 0.1% Fe;

remainder Zn.

der Pb.

The loss in ash amounted to 3.9 per cent.

What I claim is:

1. A process for working up mixed shavings of white metal and red metal, comprising heating the mixture to a temperature above the melting point of the white metal shavings but below the melting point of the red metal shavings, cooling the mixture slowly, subjecting the mixture during the cooling to a selective disintegration in which the brittle white metal particles are brought to a liner grain than the red metal particles, and separating the white metal particles from the red metal particles by mechanical methods.

2. A process for working up mixed shavings of white metal and red metal, comprising heating the mixture to a temperature above the melting point of the white metal shavings but below the melting point of the red metal shavings, cooling the mixture slowly, subjecting the mixture during the cooling to a selective disintegration in which the brittle white metal particles are brought to a finer grain than the red metal particles, and separating the white metal particles from the red metal particles by sifting.

3. A process for working up mixed shavings of white metal and red metal, compris- 7 ing heating the mixture to a temperature above the melting point of the white metal shavings but below the melting point of the red metal shavings, cooling the mixture slow ly, subjecting the mixture during the cooling to a selective disintegration by scouring, the hard red metal particles serving as scouring elements and bringing the brittle white metal particles to a finer grain than the red metal particles, and separating the white metal particles from the red metal particles by mechanical methods.

5. A process for working up mixed shavings of white metal and red metal, comprising heatingthe mixture up to the melting point of the eutectic of the white metal having the highest melting point, cooling the mixture slowly, subjecting the mixture during the cooling to a selective disintegration in which the brittle white metal particles are brought to a finer grain than the red metal particles, and separating the white metal particles from the red metal particles by mechanical methods.

6. A process for working up mixed shaV- in gs of white metal and red metal, comprising heating the mixture up to the melting point of the eutectic of the white metal having the highest melting point, cooling the mixture slowly, subjecting the mixture during the cooling to a selective disintegration by scouring, in which the brittle white metal particles are brought to a finer grain than the red metal particles, and separating the white metal particles from the red metal particles by mechanical methods.

7. A process for Worldng up mixedshavings of white metal and red metal, comprising adding to the mixture of shavings substances adapted to prevent powdered white metal from caking together and also adapted to hinder the formation of alloys between red metal and white metal, heating the mixture to a temperature above the melting point of the white metal shavings but below'the melting point of the red metal shavings,cooling the mixture slowly, subjecting the mixture during the cooling to a selective disintegration in which the brittle white metal particles are brought to a finer grain than the red metal particles, and separating the white metal particles from the red metal particles by mechanical methods.

8. A process for Working up mixed shavings of white metal and red metal, comprising adding graphite to the mixture of shavings, heating the mixture to a temperature above the melting point of the white metal shavings but below the melting point of the red metal shavings, cooling the mixture slowly, subjecting the mixture during the cooling to a selective disintegration in which the brittle white particles are brought to a finer grain than the red metal particles, and separating the white metal particles from the red metal particles by mechanical methods.

9. A process for working up mixed shavings of white metal and red metal, comprising adding to the mixture of shavings substances adapted to hinder the formation of alloys be- 0 tween red metal and white metal, heating the mixture 'to a temperature at which the white metal is completely melted, drawing oil the greater part of the molten white metal, cooling the mixture slowly, subjecting the mixture during the cooling to a selective disintegration in which the brittle white metal particles are brought to a finer grain than the red metal particles, and separating the white metal particles from the red metal particles by mechanical methods.

10. ,A process for working up mixed shavings of white metal and red metal, comprising adding to the mixture of shavings substances adapted to hinder the formation of alloys between red metal and white metal, heating the mixture to a temperature at which the white metal is completely melted, drawing off the greater part of the molten white metal, cooling the mixture slowly, subjecting the mixture during the cooling to a selective. disintegration by scouring, in which the brittle white metal particles are brought to a finer grain than the red metal particles, and separating the white metal particles from the red metal particles by mechanical methods.

11. A process for working up mixed shavings of white metal and red metal, comprising adding graphite to the mixture of shavings, heating the mixture up to the melting point of the eutectic of the White metal having the highest melting point, drawing ofi' the greater part of the molten white metal, cooling the mixture slowly, subjecting the mixture during the cooling to a selective disintegration by scouring, the hard red metal particles serving as scouring elements and bringing the brittle white metal particles to a finer grain than the red metal particles, and separating the white -,metal particles from the red metal particles by mechanical methods.

, In testimony whereof I afiix my signature.

ANTON SCHWABZ. 

